Question Leaving tmobile, Going AT&T MNVO on soon to be blocked S5

I am the first and only owner of my S5 and until tomorrow I am on T-Mobile. I have unlocked the phone successfully today, and just made a call on my roommates AT&T sim to verify. Since I have not paid the remainder of my phone off it will be blocked in the near future, and I have spent too much money with T-Mobile and their strange charges to pick up another phone with another carrier. I will wait until I get an explanation on that and see what happens with the big FTC thing going on now but until then I have read I can go AT&T MNVO in the mean time? Ideally I'd like to be one & done with my purchase and have my number ported over. The less money I have to spend the better, but I have read mixed reviews about the possibility of using a blocked phone and having network problems when switching, where the phone would work temporarily then nothing. Since all of these were threads on craigslist scams, I wondered if this applied to me? Some people have said that only goes for phones reported stolen, ie: blacklisted phones. Is there a difference between that and my blocked phone? Is there anyone that has done this or can point me in the right direction? I have read three recent threads in my research where two confirmed they were using strait talk, and one AT&T's month to month MNVO. I am looking to make a move by the end of this month and am fielding job offers as it may be out of state if I get a better one, so I'd like to not have any chance of losing my number or having my phone off for any amount of time. I don't really use a ton of a minutes, and I don't go over 2.5gb so I am pretty open to whatever works.

Any help?